The primary component of a respirator is the facepiece. The facepiece is
typically where a respirator attaches to the user, although there are also
other connections such as hoods, helmets and mouth-bits that provide
protection to the user by isolating them from the surrounding atmosphere.

The type of facepiece used affects how well the respirator seals against the
userís face which, in turn, dictates the amount of inward leakage in
negative pressure phases (when the user during the breathing cycle).